In this study, and for the first time, highly porous red mud-based geopolymer spheres were produced, through a very simple and scalable procedure, and used as lightweight aggregate in the synthesis of geopolymer composites. To further demonstrate the potential of this unexplored route, a comparison with composites containing expanded perlite and expanded vermiculite was also performed. The sample produced with 85 vol% of spheres showed the lowest geometric density (0.84 g/cm) amongst the studied composites, coupled with a suitable compressive strength (1.0 MPa), low thermal conductivity (175 mW/m K), and excellent thermal stability after exposure to 1000 °C for 2h. The much lower production temperature (80 °C), compared with the commercial expanded aggregates (above 650 °C), and the reuse of significant amounts of bauxite residue (strategy aligned with the circular economy) enables the production of eco-friendly lightweight aggregates for the building sector.

中文翻译：

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使用铝土矿渣基球体作为骨料合成地质聚合物复合材料：生产轻质建筑材料的新颖且环保的策略

在这项研究中，首次通过非常简单且可扩展的程序生产出高度多孔的赤泥基地质聚合物球，并在地质聚合物复合材料的合成中用作轻质骨料。为了进一步证明这种未开发途径的潜力，还与含有膨胀珍珠岩和膨胀蛭石的复合材料进行了比较。使用 85 vol% 球体生产的样品在所研究的复合材料中表现出最低的几何密度 (0.84 g/cm)，同时具有合适的抗压强度 (1.0 MPa)、低导热率 (175 mW/m K) 和出色的导热性能。暴露于 1000°C 2 小时后稳定性。与商业膨胀骨料（高于 650°C）相比，生产温度（80°C）低得多，并且重复利用大量铝土矿残渣（符合循环经济战略），可以生产环保的轻质骨料对于建筑行业。